Mars once had a lake fed by a river delta, NASA says new analysis of Perseverance images confirms

The escarpment the science team refers to as “Scarp a” is seen in this image captured by Perseverance rover’s Mastcam-Z instrument on Apr. 17, 2021. Credits: NASA/JPL-Caltech/MSSS

TORONTO -

NASA’s Perseverance has paid off — the first scientific analysis of images taken by the rover has shown that one of Mars’ famous craters used to be a lake, fed by small rivers, which may have gone through dramatic flooding.

Although it’s been theorized for a while that the Jezero Crater, which is now dry and wind-eroded, used to be a lake, this new analysis, published Thursday in the journal Science, sheds more light on what the crater might have looked like in its wetter days.

Perseverance’s photos were taken from the inside of the crater, and focus on a section of the crater on its western side, a fan-shaped formation as well as a prominent rock outcrop called Kodiak. Satellite images have shown that this region resembles river deltas seen on Earth, and Perseverance’s up-close perspective has confirmed this theory.

The layering of sediments and the positioning of rocks shows how water would have flowed into the lake and deposited new material.

“Never before has such well-preserved stratigraphy been visible on Mars,” Nicolas Mangold, a Perseverance scientist from the Laboratoire de Planétologie et Géodynamique in Nantes, France, and lead author of the paper, said in a NASA press release.

“This is the key observation that enables us to once and for all confirm the presence of a lake and river delta at Jezero. Getting a better understanding of the hydrology months in advance of our arrival at the delta is going to pay big dividends down the road.”

Perseverance first landed in the Jezero Crater in February, but took a rest for a few months while NASA double-checked the rover’s instruments. In that time, the rover took photos of its surroundings, including long-distance photos of the Kodiak butte.

Once those images were downloaded to Earth, researchers were able to investigate them, and could see distinct stripes of sediments in the region that they believed could only be the result of consistent flowing water going into a lake.

But that’s not the only thing the images revealed.

“If you look at these images, you’re basically staring at this epic desert landscape. It’s the most forlorn place you could ever visit,” Benjamin Weiss, professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences and a member of the analysis team, said in a Massachusetts Institute of Technology press release.

“There’s not a drop of water anywhere, and yet, here we have evidence of a very different past. Something very profound happened in the planet’s history.”

The presence of huge rocks in the upper layer of the ancient river delta indicate that not only were there gentle rivers feeding this lake, there had been flooding in the past.

Researchers theorized that there may have been a a flash flood at some point that flowed up to nine metres and moved up to 3,000 cubic metres of water per second.

“You need energetic flood conditions to carry rocks that big and heavy,” Weiss says. “It’s a special thing that may be indicative of a fundamental change in the local hydrology or perhaps the regional climate on Mars.”

Before the lake became a crater, it had wildly different heights in its life, with the size of the lake fluctuating across its lifespan. Most of these big changes in size occurred later in its life, researchers theorized.

These images are only the start. Now that Perseverance is in the crater and has confirmed that it used to be a lake, the rover will collect samples of the sediments to be analyzed later on Earth — samples that may hold signs of ancient life from this long-dead lake.